Не отображает представление в случае наличия ошибок в форме Spring Boot

При отправкe формы с ошибками, получаю 500 ошибку, вместо корректного отображения страницы представления с ошибками. Подскажите как это можно исправить, либо в каком направлении искать ошибку.

@GetMapping
    public String showCurrency(Model model) {
        List<Currency> currencies = new ArrayList<>();
        currencyRepository.findAll().forEach(i -> currencies.add(i));
            model.addAttribute("currencies",currencies);
            model.addAttribute("ConvertedCurrency", new ConvertedCurrency());
        return "convert";
    }
    @PostMapping
    public String showConvertationResult(@Valid ConvertedCurrency convertedCurrency, Errors errors) {
        if (errors.hasErrors()) {
            return "convert";
        }
        Optional<Currency> initCurrency = currencyRepository.findById(convertedCurrency.getInitCurrency());
        Optional<Currency> targetCurrency = currencyRepository.findById(convertedCurrency.getTargetCurrency());
        double amountAfterExchange = exchangeCurrency(convertedCurrency);
        convertedCurrency.setAmountAfterExchange(amountAfterExchange);
        convertedCurrency.setInitCurrency(initCurrency.get().getName());
        convertedCurrency.setTargetCurrency(targetCurrency.get().getName());
        valueTo = convertedCurrency;
        convertedCurrencyRepository.save(convertedCurrency);
        return "redirect:/convert/result";

HTML - форма.

<form method = "POST"  th:object="${ConvertedCurrency}">
        <div th:if="${#fields.hasErrors()}">
            <span class="validationError">
               Please correct the problems below and resubmit.
             </span>
        </div>
        <label>
            <select class = "CurrencyConverter" id = "0" name = "initCurrency">
            <div th:each="currency : ${currencies}">
                <option th:value = "${currency.id}" th:text="${currency.name}"></option>
            </div>
            </select>
            <input type = "text" th:field="*{amountBeforeExchange}">
            <span class="validationError"
                  th:if="${#fields.hasErrors('amountBeforeExchange')}"
                  th:errors="*{amountBeforeExchange}">error</span>
        </label>
    <br/>
        <label>
            <select class = "CurrencyConverter" id = "1" name = "targetCurrency">
            <div th:each="currency : ${currencies}">
                <option th:value = "${currency.id}" th:text="${currency.name}"></option>
            </div>
        </select>
            <input type = "hidden" th:field="*{amountAfterExchange}">
        </label>
        <p><input type="submit" value="Конвертировать"></p>
    </form>
    <form action="/history">
        <button>История конвертаций</button>
    </form>

Класс сущность

@Data
@RequiredArgsConstructor
@Entity
@Table(name="converted_currency")
public class ConvertedCurrency {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;
    @Pattern(regexp="^[0-9]*[.,]?[0-9]+$", message="Введите корректную сумму")
    private String amountBeforeExchange;
    private double amountAfterExchange;
    private String initCurrency;
    private String targetCurrency;
    private Date date;

    @PrePersist
    void createdAt() {
        this.date = new Date();
    }
}